1. Field of the Invention
The present invention relates to an image forming apparatus and, more specifically, to an image forming apparatus which determines presence/absence of ink while an ink cartridge is being moved.
2. Description of the Background Art
In an image forming apparatus, a mechanism for determining whether image formation is possible or not is important. In a thermal head printer, whether image formation is possible or not is determined by monitoring a state of conduction. In a laser printer and in an ink jet printer, whether image formation is possible or not is determined by determining presence/absence of toner and ink, respectively.
In an ink jet printer, presence/absence of the ink is determined by supplying power to an ink cartridge (conduction method), or by simulating ink jetting (jet method).
The jet method includes a method of determining presence/absence of ink by visually monitoring the state of ink jetting directly, and a method in which a specific pattern is printed on a sheet and presence/absence of the ink is determined from the printed pattern.
In the conventional method of determining presence/absence of ink by visually monitoring the state of ink jet directly includes a method in which the ink cartridge is moved to a position where a sensor is provided, outside a printing area, the ink cartridge is stopped there, the ink is jet out, and presence/absence of the ink is detected.
It should be noted, however, that the state of the ink in the ink cartridge when the cartridge is stopped is different from the state of actual printing. In the actual printing, printing is performed while the ink cartridge is moving. Therefore, the ink in the ink cartridge is influenced by acceleration. If the remaining ink is small in amount, all the remaining ink is biased on a sidewall of the ink cartridge and there is no ink left at the nozzle position. Thus, ink is not emitted. When the ink cartridge is stopped or moving at a constant speed, the ink is not influenced by acceleration. Therefore, even if only a small amount of ink is left, the ink may be emitted.
Therefore, even if it is determined by the conventional method that there is the ink, there may be cases where the ink is not emitted in actual printing operation.
Further, the nozzle position of the ink cartridge differs slightly cartridge by cartridge. Therefore, when the ink jet position for detecting presence/absence of the ink is predetermined with the ink cartridge position being used as a reference, ink jet may not be detected by a sensor when the ink is actually emitted but not jetted at a precise position. In such a case, it may be erroneously determined that the ink is used up, even when there remains sufficient ink.
Further, a mechanical loss (back lash at a gear portion and tension of a timing belt) at the time of activation may cause variation in the position of the ink cartridge itself. In such a case also, jetting of ink to a precise position is difficult, and hence it may be erroneously determined that the ink is not present even if the ink still remains.
The present invention was made to solve the above described problems and its object is to provide an image forming apparatus and a method of positioning an ink sensor, allowing accurate determination as to whether printing is possible or not in actual printing operation.
Another object of the present invention is to provide an image forming apparatus and a method of positioning an ink sensor capable of absorbing variation in nozzle position of ink cartridges to enable ink jetting at a precise position, and allowing accurate determination of ink presence/absence.
A still further object of the present invention is to provide a facsimile apparatus by which data of importance is never erased even if printing of the data should fail.
According to an aspect, the present invention provides an image forming apparatus including: a cartridge holder holding an ink cartridge filled with ink; an ink sensor provided at a known position within a recordable range of a sheet of paper; and a control unit for controlling the cartridge holder and ink cartridge such that while the cartridge holder is moved with a prescribed acceleration, the ink is jetted from a nozzle of the ink cartridge at the position of the ink sensor.
The ink is emitted to the ink sensor while the ink cartridge is being moved at a prescribed acceleration. Therefore, presence/absence of the ink can be determined under the same condition as the actual printing. Therefore, whether printing is possible or not in actual printing operation can be detected accurately.
Preferably, the image forming apparatus further includes a unit for detecting whether the ink cartridge is attached to the cartridge holder or not. The control unit includes a first unit for causing ink jet from the nozzle of the ink cartridge near the ink sensor for calculating distance between a normal position of the cartridge, holder to the ink sensor, and a unit for controlling the cartridge holder and the ink cartridge such that the ink is emitted from the nozzle of the ink cartridge at the position of the ink sensor while the cartridge holder is moved with a prescribed acceleration, based on the distance calculated by the first unit.
Accurate distance from the normal position of the cartridge holder to the ink sensor is measured by the first unit. Therefore, it is possible to jet out the ink at a precise position, absorbing variation in nozzle position among the ink cartridges, and hence it is possible to accurately determine presence/absence of the ink.
More preferably, the image forming apparatus further includes a unit for detecting whether the ink cartridge is attached to the cartridge holder or not, and a holder sensor provided between the ink sensor and the normal position of the cartridge holder for detecting passage of the cartridge holder. The control unit includes a first unit for causing ink jet from the nozzle of the ink cartridge near the ink sensor for calculating a distance from the holder sensor to the ink sensor, and a unit for controlling the cartridge holder and the ink cartridge such that the ink is emitted from the nozzle of the ink cartridge at the position of the ink sensor while the cartridge holder is moved with a prescribed acceleration, based on the distance calculated by the first unit.
The accurate distance from the holder sensor to the ink sensor is measured by the first unit. Therefore, it is possible to emit ink at a precise position, absorbing variation in nozzle position among the ink cartridges, and therefore it is possible to accurately determine ink presence/absence.
According to another aspect, the present invention provides a facsimile apparatus including a data preparing unit for preparing data to be printed; an image forming apparatus connected to the data preparing unit for forming an image of the data; and data erasing unit for erasing the data after the image is formed. The image forming apparatus includes: a cartridge holder for holding an ink cartridge filled with ink; an ink sensor provided at a known position within a recordable range of a sheet of paper; and a control unit for controlling the cartridge holder and the ink cartridge such that ink is emitted from a nozzle of the ink cartridge at a position of the ink sensor based on the data, while the cartridge holder is moved with a prescribed acceleration.
The ink is emitted to the ink sensor while the ink cartridge is moved with a prescribed acceleration. Therefore, it is possible to determine whether the ink is present/absent under the same condition as the actual printing. Therefore, it is possible to accurately determine whether printing is possible or not in the actual printing operation. Further, as it is possible to accurately determine as to whether printing is possible or not in advance, the problem of erroneous erasure of important data when printing fails can be avoided.
According to a still further aspect, the present invention provides a method of positioning an ink sensor, used in an image forming apparatus including a cartridge holder for holding an ink cartridge filled with ink, an ink sensor provided at a known position within a recordable range of a sheet of paper, and a unit for determining whether the ink cartridge is attached to the cartridge holder. The method of positioning the ink sensor includes the steps of: when the ink cartridge is exchanged, moving the cartridge holder from a normal position of the cartridge holder to approximately a position of the ink sensor; causing ink jetting from the nozzle of the ink cartridge while swinging the cartridge holder over a prescribed width; detecting ink jetting by the ink sensor; and calculating a distance from the normal position of the cartridge holder to the ink sensor in accordance with the result of detecting by the ink sensor.
As the ink is emitted while the cartridge holder swings near the ink sensor, accurate distance between the normal position the cartridge holder to the ink sensor can be found. Therefore, it is possible to find an accurate ink sensor position, absorbing variation of the nozzle position among the ink cartridges.
According to a still further aspect, the present invention provides a method of positioning an ink sensor used for an image forming apparatus including an ink cartridge filled with ink, a cartridge holder holding the ink cartridge, an ink sensor provided at a known position within a recordable range of a sheet, a holder sensor provided between the ink sensor and a normal position of the cartridge holder for detecting passage of the cartridge holder, and a unit for detecting whether the ink cartridge is attached to the cartridge holder. The method of positioning the ink sensor includes the steps of: when the ink cartridge is exchanged, moving the cartridge holder from the normal position of the cartridge holder to approximate position of the ink sensor; detecting, by the holder sensor, passage of the cartridge holder; emitting ink from a nozzle of the ink cartridge while swinging the cartridge holder over a prescribed width, detecting by the ink sensor, jetting of the ink; and calculating distance between the holder sensor to the ink sensor in accordance with the result of detection by the ink sensor.
As the ink is emitted while the cartridge holder swings near the ink sensor, accurate distance from the holder sensor to the ink sensor is calculated. Therefore, it is possible to find accurate ink sensor position, absorbing variation of nozzle position among the ink cartridges.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.